Availability and reliability. SANs also provide technologies that enhance system and data availability and reliability. Many of these technologies aren't new to SANs but are widely implemented as standard SAN features.
Volume or LUN cloning and snapshots are examples of key availability technologies. Implemented at the controller level, these features create redundant data volumes for recovery use in Windows servers and applications such as Exchange and SQL Server. Clones are completely redundant copies of data, whereas snapshots are point-in-time block mappings of data volumes. (Snapshots aren't completely redundant data sets but a combination of changed and unchanged data blocks within a storage pool.)
Neither Windows 2000 nor Exchange offer native support for snapshot or clone technology, but Win.NET Server will feature VSS, which provides native OS support for clone and snapshot technologies. Hardware and software vendors of snapshot and clone technology products will be able to develop VSS providers to plug their products into the VSS framework. Applications will use the VSS services through writers, which implement application-specific recovery packages.
Other interesting availability and reliability technologies available with SANs include Remote Data Replication (essentially, remote cloning) and SAN-attached backup (the ability to attach a backup server directly to the SAN rather than to the LAN or server attachment). The number of rapid-recovery solutions and capabilities that vendors can build with SAN technologies in the Windows environment are endless and are exactly what Windows administrators are clamoring for to increase system and data availability.
Manageability and lower TCO. Managing individual servers with individual storage systems is fairly simple as long as the number of servers is small. However, as the number of servers and the amount of data housed on these servers grow, IT departments wonder how they will manage the systems.
IT is turning to SAN technologies to simplify storage management and to aid in consolidation efforts. With features such as Selective Storage Presentation (SSP) and virtualization, administrators can leverage SANs to bring their data under centralized control and management. Selective storage presentation and virtualization provide a secure and manageable view of the physical storage abstracted into solution-specific storage units. These SAN features also facilitate data and storage provisioning and general Storage Resource Management (SRM).
Enterprise storage facilities will move from disparate systems owned by OSs and applications to an enterprise pool of storage that users can dynamically provision based on user and application requirements—a huge benefit to server and service consolidation projects that must aggregate large amounts of data and storage for one large server or application. Further advancements in SRM and new technologies such as the SCSI over IP (iSCSI) protocol will advance SANs' ability to provide increased manageability and lower the TCO for SAN deployment and operation in both large and small enterprises.
Windows administrators need the benefits of SAN and NAS storage technologies. With these technologies' advances and proliferation, the costs and barriers to deployment should eventually disappear. Microsoft is also embracing these technologies on the Windows platform (particularly in Win.NET Server) and in .NET Enterprise Server products such as Exchange and SQL Server. It's time for Windows IT departments to enjoy the benefits of Windows with SANs—or as the French would say, "Windows avec SANs."
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